4. ANALYSIS OF FACTORS INVOLVED IN SYMBIOSIS
85
only available information is that the verruciform cells of the mesozoan
Pseudicyema truncatum are said to include lipoproteins (Hyman,
1940a). .As in the case of carbohydrates, only the larval trematodes have
been studied to any extent; then again, the information pertains
primarily to a few species parasitic in freshwater gastropods although
the findings of Cheng (1965b) on Bucephalus sp. in the American
oyster, Crassostrea virginica, suggest that the general pattern is the
same in marine and freshwater species. For this reason, the literature is
briefly reviewed at this point with emphasis placed on function.
The occurrence of lipids in intramolluscan larval trematodes is known
for a few species. In miracidia fats occur, although not in as large a
quantity as glycogen (Axmann, 1947 ; von Brand, 1952). No information is yet available as to whether the stored fats in miracidia, which are
generally the pre-molluscan, free-swimming stage or are found in the
alimentary tract if eggs are ingested intact, are employed as an energy
source. Purely from the speculative standpoint, it would appear that
among the free-swimming species the availability of oxygen would
suggest the utilization of lipids as among free-swimming cercariae.
Ginecinskij (1961) has studied the occurrence of lipids in eight
species of freshwater larval trematodes. It is of interest to note that
she has found that the quantity of lipids present in sporocyst walls is
directly correlated with the sites which they occupy within the molluscan hosts. Those situated on the surfaces of the host’s intestine are
almost completely devoid of lipids as are those located between organs.
However, the sporocysts of Cotylurus brevis and Cercaria spinulosa,
which are embedded in their hosts’ hepatopancreas, are rich in
fats.
Cheng and Snyder (1962c), while studying the lipid composition of
Glypthelmins pennsylvaniensis, have found fatty acids adhering to and
on the interior of the sporocyst wall, thus suggesting the permeation of
fatty acid molecules. For this reason, Cheng (1963d) questioned whether
the 1ipid.s found by Ginecinskij in sporocyst walls were stationary or
transient. That fatty acids occur in sporocyst walls has been confirmed
by Cheng (1965b) who found them in the sporocyst walls of Bucephalus
sp. parasitizing oysters. The question raised in 1963 appears to be
partially answered in 1965 when I found neutral fats in the sporocyst
wall of Bucephalus, since although fatty acids are believed to be capable
of permeating sporocyst walls, neutral fats are not. Hence, the neutral
fats found in Bucephalus sporocyst walls most probably are not transient. It is unfortunate that Ginecinskij’s studies only involved the use of
Sudan black B which does not permit differentiation between neutral
fats and fatty acids.
85
only available information is that the verruciform cells of the mesozoan
Pseudicyema truncatum are said to include lipoproteins (Hyman,
1940a). .As in the case of carbohydrates, only the larval trematodes have
been studied to any extent; then again, the information pertains
primarily to a few species parasitic in freshwater gastropods although
the findings of Cheng (1965b) on Bucephalus sp. in the American
oyster, Crassostrea virginica, suggest that the general pattern is the
same in marine and freshwater species. For this reason, the literature is
briefly reviewed at this point with emphasis placed on function.
The occurrence of lipids in intramolluscan larval trematodes is known
for a few species. In miracidia fats occur, although not in as large a
quantity as glycogen (Axmann, 1947 ; von Brand, 1952). No information is yet available as to whether the stored fats in miracidia, which are
generally the pre-molluscan, free-swimming stage or are found in the
alimentary tract if eggs are ingested intact, are employed as an energy
source. Purely from the speculative standpoint, it would appear that
among the free-swimming species the availability of oxygen would
suggest the utilization of lipids as among free-swimming cercariae.
Ginecinskij (1961) has studied the occurrence of lipids in eight
species of freshwater larval trematodes. It is of interest to note that
she has found that the quantity of lipids present in sporocyst walls is
directly correlated with the sites which they occupy within the molluscan hosts. Those situated on the surfaces of the host’s intestine are
almost completely devoid of lipids as are those located between organs.
However, the sporocysts of Cotylurus brevis and Cercaria spinulosa,
which are embedded in their hosts’ hepatopancreas, are rich in
fats.
Cheng and Snyder (1962c), while studying the lipid composition of
Glypthelmins pennsylvaniensis, have found fatty acids adhering to and
on the interior of the sporocyst wall, thus suggesting the permeation of
fatty acid molecules. For this reason, Cheng (1963d) questioned whether
the 1ipid.s found by Ginecinskij in sporocyst walls were stationary or
transient. That fatty acids occur in sporocyst walls has been confirmed
by Cheng (1965b) who found them in the sporocyst walls of Bucephalus
sp. parasitizing oysters. The question raised in 1963 appears to be
partially answered in 1965 when I found neutral fats in the sporocyst
wall of Bucephalus, since although fatty acids are believed to be capable
of permeating sporocyst walls, neutral fats are not. Hence, the neutral
fats found in Bucephalus sporocyst walls most probably are not transient. It is unfortunate that Ginecinskij’s studies only involved the use of
Sudan black B which does not permit differentiation between neutral
fats and fatty acids.